// Copyright 2008 Google Inc.
// 
// Licensed under the Apache License, Version 2.0 (the "License");
// you may not use this file except in compliance with the License.
// You may obtain a copy of the License at
// 
//      http://www.apache.org/licenses/LICENSE-2.0
// 
// Unless required by applicable law or agreed to in writing, software
// distributed under the License is distributed on an "AS IS" BASIS,
// WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
// See the License for the specific language governing permissions and
// limitations under the License.

package com.google.calculator.tree;

/**
 * Tree leaf for variable.
 * 
 * @author tulaurent@gmail.com (Laurent Tu)
 *
 */
public class TerminalVariable implements Tree {

  private String variableName;

  public TerminalVariable(String variableName) {
    this.variableName = variableName;
  }
  
  public double evaluate(EvaluationContext context) {
    Double value = context.variables.get(variableName);
    if (value != null) {
      return value;
    }
    // TODO(Laurent): raise an exception.
    return 0;
  }

}
